1. Field of the Invention
The present invention relates to a jet engine for a high-speed aircraft, and more particularly, a jet engine suitable for propelling an aircraft flying at either supersonic speed or subsonic speed.
2. Description of the Related Art
In a supersonic aircraft, the exhaust gas must be raised to high temperature and high velocity, in order to obtain high thrust for take-off or supersonic flight. However, in a conventional turbojet engine, it has not been possible to obtain the exhaust gas temperature required for supersonic flight, as a result of limitations on the turbine inlet temperature.
On the other hand, with a view to achieving high temperature and high velocity of the exhaust gas, turbojet engines with afterburners and turbofan engines with afterburners have been developed for practical use. However, an engine with an afterburner has a disadvantage in that the noise generated by the engine is excessively loud, because the speed of the exhaust gas is very high, particularly at take-off.
Therefore, in order to reduce noise at take-off, while obtaining a high exhaust gas temperature during supersonic flight, engines incorporating a variable mechanism for changing, for instance, the bypass ratio inside the engine, have been proposed and researched, but satisfactory results have not yet been obtained. Moreover, U.S. Pat. No. 3,841,091 discloses a jet engine wherein two turbojet engines are coupled, one in front of the other, and bypass air is fed to one of the turbojet engines by switching the air path, but this does not enable light weight or a more compact size to be achieved.
The present invention was devised with the foregoing in view, an object being to provide a jet engine providing high thrust, while reducing the problems of noise and weight at take-off, for an aircraft flying at high speed, in particular, either supersonic speed or subsonic speed.
In order to achieve the aforementioned object, the jet engine for a high-speed aircraft according to the present invention is a jet engine for a high-speed aircraft, comprising: a front engine consisting of a turbofan engine; and a rear engine consisting of at least one turbofan engine or turbojet engine disposed to the rear of the front engine; wherein the rear engine is coupled to a bypass duct of the front engine by means of a tube, and the rear engine obtains thrust by raising the pressure and temperature of the bypass air from the front engine.
According to the foregoing composition, it is possible to raise the temperature and pressure of bypass air from a low-noise turbofan engine by use of a separately disposed single or plurality of turbojet engines or turbofan engines, and therefore, because the bypass air can be discharged without the temperature or pressure thereof being further raised during take-off, it is possible to achieve a jet engine for a supersonic aircraft which enables take-off at low noise level. The aforementioned turbofan engine may be a front fan-type or after fan-type engine.
A further jet engine for a high-speed aircraft according to the present invention seeking to resolve the aforementioned problems is a jet engine for a high-speed aircraft, comprising: a front engine consisting of a turbofan engine; and a rear engine consisting of at least one turbofan engine or turbojet engine disposed to the rear of the front engine; the rear engine further comprising intake air switching means capable of switching the rear engine between a bypass air intake state, wherein the rear engine takes in bypass air from the front engine, and an external air intake state, wherein the rear engine takes in external air directly.
The aforementioned intake air switching means may be accomplished in a variety of ways, for example, by tube switching means for switching a tube supplying bypass air from the front engine to the rear engine, external air being taken in by the rear engine via an auxiliary air inlet and thrust being obtained by means of the engine air flow being increased by the rear engine in combination with the front engine, when the pipe switching means switches to the external air intake position.
Furthermore, the intake air switching means may be constituted by rear engine displacing means for displacing the rear engine to a position outside the projected area of the front face of the front engine, external air being taken in by the rear engine and thrust being obtained by means of the engine air flow being increased by the rear engine in combination with the front engine, when the rear engine displacing means moves the rear engine to a position outside the projected area of the front face of the front engine.
The intake air switching means may also be constituted by front engine displacing means for displacing the front engine to a position outside the projected area of the front face of the rear engine. In this case, when the front engine displacing means moves the front engine to a position outside the projected area of the front face of the rear engine, a relatively large thrust can be obtained by means of the engine exhaust being increased, in a similar manner to a case where the rear engine is moved.